A known and prior art turbine engine design includes stages, the principal components of which comprise a plurality of metal vanes or blades arranged in spaced-apart, radially-extending relationship with a circular mounting band, usually comprising two half circular parts which are assembled together during the construction of the engine.
According to known assembly techniques, the blades are assembled with the mounting bands by preforming a plurality of slots or holes in a mounting band, inserting the end tangs of the preformed blades in the slots and clipping the ends of the tangs which project through the outer surface of the mounting bands to hold the blades in place prior to and during a brazing operation. The holes or slots in the mounting stock are generally made somewhat larger than the tangs of the blades so that a loose or "sloppy" fit between the blades and the mounting stock exists. The assemblies are placed in a jig and each blade is individually adjusted in its position relative to the mounting band, the clip being required to hold the blade in the proper location prior to and during the brazing operation. The assemblies cannot withstand rough treatment between final adjustment and brazing since such rough treatment will disturb the precise location of one or more of the blades.
Another problem area associated with the prior art assembly technique lies in the addition of the brazing material to the assembly. The latest prior art technique is to use a small hairpin-shaped length of brazing wire and effectively clip this small piece of wire around the edge of the turbine blade immediately adjacent the inside surface of the mounting band. The article is then placed in a furnace where the brazing material melts and runs by capillary action into the interstices between the blade, blade tang and mounting stock material.
An alternative to the use of the clip is the use of a manual device similar to a hypodermic needle to inject a small amount of brazing material, preferably mixed with flux onto the proper location of the blade immediately prior to placing the turbine component in a brazing furnace.
Both operations depend on manual application and, therefore, involve costly labor.